1. Field of the Invention
The invention relates generally to electrical font cartridges and more particularly to electrical font cartridges for use in printers.
2. Description of the Prior Art
Laser printers and ink jet printers have become increasingly popular. These printers, which provide a high quality printed product, are often used in connection with personal computers to provide desk top publishing capability. Hewlett Packard Company (HP) sells a line of such laser printers under the trademark "LaserJet".
These printers do not have a mechanical impact head. Instead, in the case of the laser printers, printed characters are formed by the interaction of a laser beam and the black powder "toner" that makes the actual images. Many different types of fonts may be specified to the printer. The different fonts are designated by a font selection parameter which consists of several fields of characters. Typically, a laser printer has an internal memory which stores two or more of the most common font styles. The printers also have at least one slot for receiving a font cartridge. The font cartridges have memories which contain additional fonts.
HP sells a number of font cartridges, labelled A-Z for its line of laser printers. Each cartridge typically contains between three and eighteen fonts. Some of the newer laser printers also have multiple slots for receiving a number of font cartridges at the same time in order to provide the printer with a greater number of fonts from which to select.
In operation, the printer reads the font information in the font cartridges into its own internal memory for use during printing. The printers are limited in the number of fonts and the amount of cartridge memory which they may access at any one time because of the limits of the printer internal memory and control. For example, one popular model of the HP LaserJet printer has two cartridge slots, but it can recognize a maximum of only one hundred thirty six different fonts between the two cartridges and the maximum memory per cartridge is limited by the printer's memory address capacity to two megabytes. If either the number of different fonts or the total memory inside the two cartridges exceeds this limit, then the printer will not function properly. Due to the large number of different types of fonts, additional cartridges must be made available and substituted into the printer's cartridge slots as necessary. This constant changing of cartridges is very time consuming and requires the user to maintain a library of different cartridges.